This application relates to the art of entraining vehicles that move on castors so that trailing vehicles will follow the curvilinear path established by a towing force. The invention is particularly applicable to hospital carts and gurneys, although it will be appreciated that the invention has broader applicability to most types of castorwheel vehicles.
It is known in the art that for maximum stability and flexibility of towing, the lead wheels of any towed vehicle should be free to rotate, while the rear wheels should be locked in a straight orientation. Thus, various methods of manually locking castorwheels in a fixed position are known in the art. These methods do not readily lend themselves to entraining multiple vehicles, however, since they require manual intervention to lock and unlock the castors, at least at the individual vehicle level, and often at the level of each castorwheel.
Moreover, the methods employed for locking the castors in desired configurations frequently result in a restricted range of motion for the castors when the vehicle is returned to its primary use as a single unit. When operating alone, maximum maneuverability of each vehicle requires that all castorwheels be allowed to swivel through a full 360 degrees of motion.
Thus, it is desirable to have a locking mechanism that allows each castor of a vehicle, while operating alone, to swivel freely, through a 360 degree range of motion, yet automatically provides for appropriate locking of trailing castors when the vehicle is entrained. It is also desirable to be able to apply towing force from either end of a train of vehicles, with automatic interchange of the leading and trailing castor configuration.